Jet Set Willy was first developped for the Sinclair ZX Spectrum in 1984 as a sequel to the successful Manic Miner, and is now regarded as one of the most classic platform games ever. It was ported to a large number of 8-bit consoles at the time.

A 2D platform action game like Manic Miner, in Jet Set Willy the player controls the rather flat-faced character Miner Willy, jumping around on screens filled with enemies that move on the screen following a certain scheme, and that will kill on touch. As Willy can't be controlled in mid-air, the game is all about high-precision jumps to avoid the enemies and collect the blinking items on screen.

Unlike Manic Miner, which is about clearing one screen after the other, in Jet Set Willy the player explores all rooms in a vast mansion consisting of no less than 60 rooms, and the goal of the game is to collect all items in all rooms, or the housekeeper Maria won't let Willy go to bed. This has to be done before midnight, which accounts for 5 hours of playing time as the game starts at 7 PM.

If Willy is killed, he loses one life and is returned to exactly where he entered the room, keeping any momentum, which can be disastrous if he enters a room in a way that will get him killed; this will cause a chain-reaction of losing all remaining lives. This, combined with the fact that all rooms require a meticulous jumping, has earned Jet Set Willy the rumour of being one of the most difficult platform games ever released.

The game was planned to be released on the Amiga and Atari ST in 1989, but near completion, Software Projects cancelled the release as they regarded JSW as being out of its time. The Atari release was nonetheless inofficially spread, and is now available as a free download for the platform.

Jet Set Willy was revived by the developper Retrospec in 1999, porting it to DOS and later Windows and Macintosh as an official free download. This "Jet Set Willy PC" is a direct Spectrum port, keeping the exact same sprites only decorated in multicolour.